Q.1 Which type of bioreactor is most commonly used for the production of monoclonal antibodies in pharmaceutical industry?
Stirred‑tank bioreactor
Air‑lift bioreactor
Packed‑bed reactor
Membrane bioreactor
Explanation - Stirred‑tank bioreactors provide uniform mixing, precise temperature and pH control, which are essential for high‑yield monoclonal antibody production.
Correct answer is: Stirred‑tank bioreactor
Q.2 In a bioreactor used for tissue engineering, which electrical component is critical for maintaining a uniform electric field across the scaffold?
Variable frequency drive (VFD)
Charge pump
Plate electrode array with a constant voltage source
Step‑down transformer
Explanation - A constant voltage source applied to a plate electrode array creates a stable electric field that can stimulate cell growth uniformly across the scaffold.
Correct answer is: Plate electrode array with a constant voltage source
Q.3 What is the primary advantage of using a perfusion bioreactor for culturing hepatocytes compared to a batch bioreactor?
Higher shear stress improves cell adhesion
Continuous removal of toxic metabolites and supply of fresh media
Simpler control circuitry
Lower power consumption
Explanation - Perfusion systems continuously replace spent media, maintaining a healthier environment for hepatocytes and improving long‑term functionality.
Correct answer is: Continuous removal of toxic metabolites and supply of fresh media
Q.4 Which sensor is most suitable for real‑time monitoring of dissolved oxygen in a mammalian cell bioreactor?
Thermocouple
Clark‑type electrochemical sensor
pH glass electrode
Capacitive humidity sensor
Explanation - Clark‑type sensors provide accurate dissolved oxygen measurements and are compatible with sterile bioprocess environments.
Correct answer is: Clark‑type electrochemical sensor
Q.5 In the context of bioreactor control systems, what does PID stand for?
Power‑Induction‑Drive
Proportional‑Integral‑Derivative
Pulse‑Input‑Device
Pressure‑Inlet‑Discharge
Explanation - PID controllers adjust process variables by calculating proportional, integral, and derivative terms to minimize error.
Correct answer is: Proportional‑Integral‑Derivative
Q.6 Which bioreactor design is most appropriate for large‑scale production of biofuels using yeast?
Bubble column reactor
Stirred‑tank reactor with high shear impellers
Photobioreactor
Wave‑motion bioreactor
Explanation - High shear impellers ensure adequate mixing and oxygen transfer for yeast metabolism in biofuel production.
Correct answer is: Stirred‑tank reactor with high shear impellers
Q.7 What is the role of a microcontroller in a lab‑scale bioreactor system?
Generate high‑voltage sparks for sterilization
Control temperature, pH, and agitation via sensor feedback
Supply nutrients directly to the culture
Act as a power inverter for AC motors
Explanation - Microcontrollers process sensor data and adjust actuators to maintain optimal culture conditions.
Correct answer is: Control temperature, pH, and agitation via sensor feedback
Q.8 Which type of bioreactor is specifically designed for culturing photosynthetic microorganisms?
CSTR (Continuous Stirred‑Tank Reactor)
Photobioreactor
Anaerobic digester
Membrane bioreactor
Explanation - Photobioreactors provide controlled illumination, essential for photosynthetic growth.
Correct answer is: Photobioreactor
Q.9 In a bioreactor used for vaccine production, why is temperature ramping important during the fermentation phase?
To increase viscosity of the medium
To trigger expression of temperature‑sensitive viral antigens
To reduce power consumption
To enhance oxygen solubility
Explanation - Some vaccine strains are engineered to express antigens only at specific temperatures, ensuring high yield and safety.
Correct answer is: To trigger expression of temperature‑sensitive viral antigens
Q.10 Which electrical safety standard is most relevant for bioreactor equipment used in a GMP (Good Manufacturing Practice) facility?
ISO 9001
IEC 60601‑1
IEEE 802.11
UL 94
Explanation - IEC 60601‑1 addresses safety requirements for medical electrical equipment, applicable to GMP bioprocessing devices.
Correct answer is: IEC 60601‑1
Q.11 What advantage does a single‑use (disposable) bioreactor provide in cell therapy manufacturing?
Higher maximum volume capacity
Elimination of cleaning and sterilization validation
Improved electrical efficiency
Ability to operate at higher pressures
Explanation - Single‑use systems reduce cross‑contamination risk and speed up change‑over between batches, crucial for personalized therapies.
Correct answer is: Elimination of cleaning and sterilization validation
Q.12 Which parameter is directly affected by the impeller speed (rpm) in a stirred‑tank bioreactor?
pH setpoint
Dissolved oxygen transfer rate
Medium osmolarity
Light intensity
Explanation - Higher impeller speeds improve mixing and gas‑liquid mass transfer, increasing dissolved oxygen availability.
Correct answer is: Dissolved oxygen transfer rate
Q.13 For a bioreactor used in 3‑D bioprinting of cartilage tissue, which electrical signal is most commonly applied to enhance chondrogenic differentiation?
High‑frequency ultrasonic waves
Low‑frequency pulsed electric fields (PEF)
Continuous DC voltage
Radio‑frequency (RF) heating
Explanation - PEF stimulates cellular pathways that promote cartilage matrix production without causing thermal damage.
Correct answer is: Low‑frequency pulsed electric fields (PEF)
Q.14 Which control strategy is best suited for maintaining a constant pH in a large‑scale bacterial fermentation bioreactor?
Open‑loop feedforward control
On‑off (bang‑bang) control
PID control with acid/base addition
Manual adjustment by operator
Explanation - PID provides continuous, precise correction of pH deviations by automatically dosing acid or base.
Correct answer is: PID control with acid/base addition
Q.15 In a bioreactor used for production of recombinant proteins, why is it important to monitor the redox potential (ORP)?
It directly measures protein concentration
It indicates the oxidative state influencing protein folding
It controls temperature automatically
It replaces the need for dissolved oxygen measurement
Explanation - ORP reflects the cellular environment’s oxidative conditions, which can affect disulfide bond formation in proteins.
Correct answer is: It indicates the oxidative state influencing protein folding
Q.16 Which type of actuator is typically used to adjust the flow rate of media in a bioreactor's feed line?
Stepper motor‑driven syringe pump
Hydraulic cylinder
Piezoelectric buzzer
Thermoelectric cooler
Explanation - Stepper motors provide precise, repeatable positioning, enabling accurate volumetric flow control in feed lines.
Correct answer is: Stepper motor‑driven syringe pump
Q.17 What is the main purpose of using a gas‑sparging system in an aerobic bioreactor?
To sterilize the culture medium
To provide carbon dioxide for pH control
To increase dissolved oxygen levels for microbial growth
To create foam for cell protection
Explanation - Air or oxygen sparging introduces gas bubbles that dissolve, raising the dissolved oxygen concentration needed for aerobic metabolism.
Correct answer is: To increase dissolved oxygen levels for microbial growth
Q.18 Which computational method is commonly used to model fluid dynamics inside a bioreactor for scale‑up studies?
Finite Element Analysis (FEA)
Computational Fluid Dynamics (CFD)
Monte Carlo Simulation
Discrete Event Simulation
Explanation - CFD simulates fluid flow, mixing patterns, and mass transfer, aiding in the design and scale‑up of bioreactors.
Correct answer is: Computational Fluid Dynamics (CFD)
Q.19 In a bioreactor used for stem cell expansion, why is low shear stress important?
It prevents cell aggregation
It enhances nutrient diffusion
It reduces damage to delicate cell membranes
It increases temperature uniformity
Explanation - Stem cells are sensitive; excessive shear can rupture membranes, compromising viability and differentiation potential.
Correct answer is: It reduces damage to delicate cell membranes
Q.20 Which of the following bioreactor configurations enables simultaneous cultivation and product separation in a single unit?
Fed‑batch reactor
Membrane bioreactor
Batch reactor
Air‑lift reactor
Explanation - Membrane modules allow continuous removal of product (e.g., metabolites) while retaining cells inside the reactor.
Correct answer is: Membrane bioreactor
Q.21 For a bioreactor that employs electroporation to introduce DNA into bacterial cells, which electrical parameter must be carefully controlled?
Frequency of the AC signal
Pulse voltage and duration
RMS current
Phase angle of the waveform
Explanation - Electroporation efficiency depends on achieving a specific electric field strength for a defined time to create transient pores.
Correct answer is: Pulse voltage and duration
Q.22 What is the purpose of using a torque sensor on the drive shaft of a bioreactor impeller?
To monitor the power consumption and detect changes in broth viscosity
To regulate the temperature of the motor
To control the pH of the culture medium
To generate a backup power supply
Explanation - Torque correlates with the resistance offered by the culture, indicating viscosity changes due to cell growth or fouling.
Correct answer is: To monitor the power consumption and detect changes in broth viscosity
Q.23 Which type of bioreactor is best suited for cultivating anaerobic bacteria that produce biogas?
Aerobic stirred‑tank reactor
Anaerobic digester
Photobioreactor
Membrane bioreactor
Explanation - Anaerobic digesters provide oxygen‑free environments ideal for methanogenic bacteria that generate biogas.
Correct answer is: Anaerobic digester
Q.24 In the context of bioreactor instrumentation, what does the term 'dead time' refer to?
The time required for the reactor to reach operating temperature
The delay between a sensor measurement and its availability to the controller
The duration of a cleaning cycle
The interval between two feed pulses
Explanation - Dead time can degrade control performance and must be minimized in fast‑responding bioprocesses.
Correct answer is: The delay between a sensor measurement and its availability to the controller
Q.25 Which of the following is a key advantage of using a digital twin of a bioreactor in process development?
Eliminates the need for any physical experiments
Provides real‑time predictive analytics for scale‑up and optimization
Reduces the electrical power consumption by 50%
Automatically generates regulatory documentation
Explanation - Digital twins simulate the bioprocess, allowing virtual testing of conditions before physical implementation.
Correct answer is: Provides real‑time predictive analytics for scale‑up and optimization
Q.26 When designing a control algorithm for a bioreactor that produces insulin, which performance metric is most critical?
Minimizing temperature fluctuations
Maximizing oxygen transfer rate
Maintaining a steady glucose concentration
Ensuring low power factor
Explanation - Glucose is the primary carbon source; its concentration directly influences insulin expression levels.
Correct answer is: Maintaining a steady glucose concentration
Q.27 Which power electronics device is commonly used to drive a three‑phase AC motor for bioreactor agitation?
H‑bridge inverter
Buck‑boost converter
Three‑phase VFD (Variable Frequency Drive)
Flyback transformer
Explanation - VFDs allow precise control of motor speed and torque, essential for adjusting mixing intensity.
Correct answer is: Three‑phase VFD (Variable Frequency Drive)
Q.28 In a continuous bioprocess, what does the term 'steady‑state' imply?
All parameters are constant over time
The reactor is shut down for cleaning
The temperature is at its highest point
The impeller speed is zero
Explanation - At steady‑state, inputs equal outputs, and variables such as biomass, substrate, and product concentrations remain unchanged.
Correct answer is: All parameters are constant over time
Q.29 Which of the following is a common method to prevent foam formation in a bioreactor cultivating yeast?
Increasing impeller speed
Adding antifoam agents
Reducing temperature
Applying a high voltage across the broth
Explanation - Antifoam chemicals reduce surface tension, suppressing foam that can cause over‑flows or sensor errors.
Correct answer is: Adding antifoam agents
Q.30 For a bioreactor used in the production of viral vectors for gene therapy, which biosafety level (BSL) is typically required?
BSL‑1
BSL‑2
BSL‑3
BSL‑4
Explanation - Viral vector production usually involves recombinant viruses that require BSL‑2 containment to protect personnel.
Correct answer is: BSL‑2
Q.31 Which analytical technique can be integrated into a bioreactor system for online monitoring of metabolite concentrations?
Gas chromatography‑mass spectrometry (GC‑MS)
Near‑infrared (NIR) spectroscopy
Western blotting
ELISA
Explanation - NIR probes provide rapid, non‑invasive measurements of key metabolites such as glucose and lactate.
Correct answer is: Near‑infrared (NIR) spectroscopy
Q.32 What is the main function of a heat exchanger attached to a bioreactor's cooling jacket?
To sterilize the medium
To maintain the desired temperature by removing excess heat
To increase dissolved oxygen
To regulate pH
Explanation - Biological reactions generate heat; the cooling jacket removes it to keep the culture at optimal temperature.
Correct answer is: To maintain the desired temperature by removing excess heat
Q.33 In a bioreactor used for producing recombinant DNA vaccines, why is it essential to monitor the conductivity of the culture medium?
It indicates the concentration of ions and can signal nutrient depletion
It directly measures DNA concentration
It controls the impeller speed
It prevents electromagnetic interference
Explanation - Conductivity reflects ionic strength; a drop may indicate depletion of salts or nutrients needed for growth.
Correct answer is: It indicates the concentration of ions and can signal nutrient depletion
Q.34 Which type of bioreactor is most suitable for high‑cell‑density cultivation of CHO cells used in monoclonal antibody production?
Packed‑bed reactor
Wave‑motion bioreactor
Air‑lift reactor
Stirred‑tank bioreactor with perfusion
Explanation - Perfusion maintains nutrient supply and waste removal, supporting high cell densities required for antibody yields.
Correct answer is: Stirred‑tank bioreactor with perfusion
Q.35 Which of the following control loops would be most appropriate for maintaining dissolved oxygen at a setpoint in a high‑density mammalian cell culture?
Cascade control: primary loop for agitation speed, secondary loop for oxygen sparge rate
On‑off control of gas flow only
Manual adjustment by operator
Feedforward control based on temperature
Explanation - Cascade control improves oxygen transfer by coordinating agitation (mass transfer) and gas flow.
Correct answer is: Cascade control: primary loop for agitation speed, secondary loop for oxygen sparge rate
Q.36 What is the primary reason for using a stainless‑steel 316L grade for bioreactor vessels?
Higher electrical conductivity
Superior corrosion resistance and biocompatibility
Lower cost compared to plastic
Better magnetic properties
Explanation - 316L stainless steel resists corrosion from media components and can be sterilized repeatedly.
Correct answer is: Superior corrosion resistance and biocompatibility
Q.37 In an electrically powered bioreactor, what is the purpose of a ground fault circuit interrupter (GFCI)?
To maintain constant voltage supply
To detect and interrupt leakage currents that could cause electric shock
To regulate temperature
To control pH automatically
Explanation - GFCIs enhance safety by shutting off power when leakage exceeds a safe threshold, vital in wet lab environments.
Correct answer is: To detect and interrupt leakage currents that could cause electric shock
Q.38 Which bioreactor configuration allows for the simultaneous growth of aerobic and anaerobic microorganisms in separate compartments?
Dual‑chamber bioreactor with a gas‑tight membrane
Single‑compartment stirred‑tank reactor
Air‑lift reactor
Photobioreactor
Explanation - The membrane separates the chambers, permitting distinct gas environments while allowing nutrient exchange.
Correct answer is: Dual‑chamber bioreactor with a gas‑tight membrane
Q.39 What is the effect of increasing the dissolved CO₂ concentration in a plant cell suspension culture?
It raises the pH of the medium
It inhibits photosynthesis
It enhances growth by providing a carbon source
It reduces temperature stability
Explanation - CO₂ serves as a carbon substrate for photosynthetic pathways, promoting cell proliferation.
Correct answer is: It enhances growth by providing a carbon source
Q.40 Which of the following is a typical indicator that a bioreactor's impeller is causing excessive shear stress?
Increased dissolved oxygen levels
Reduced cell viability and increased cell lysis
Higher temperature readings
Lower pH values
Explanation - High shear can physically damage cells, leading to loss of viability and release of intracellular contents.
Correct answer is: Reduced cell viability and increased cell lysis
Q.41 In the design of an electric heater for a bioreactor, which parameter determines the heating element's power rating?
Voltage × Current (P = V·I)
Resistance × Capacitance
Frequency × Inductance
Impedance × Phase angle
Explanation - Electrical power is the product of voltage and current; this determines the heating capacity needed.
Correct answer is: Voltage × Current (P = V·I)
Q.42 Why is an insulated jacket used around some bioreactors instead of a cooling jacket?
To maintain low temperature without active cooling
To reduce heat loss and keep the reactor at a stable elevated temperature
To provide a space for sensor placement
To increase the reactor's pressure rating
Explanation - Insulation minimizes heat exchange with the environment, essential for thermophilic cultures that require higher temperatures.
Correct answer is: To reduce heat loss and keep the reactor at a stable elevated temperature
Q.43 Which parameter is most directly affected by the use of a peristaltic pump for feeding substrate into a bioreactor?
pH stability
Feed rate precision
Oxygen transfer efficiency
Impeller torque
Explanation - Peristaltic pumps provide accurate, controllable flow rates, essential for substrate feeding strategies.
Correct answer is: Feed rate precision
Q.44 When scaling up a bioreactor from lab‑scale (10 L) to pilot‑scale (1000 L), which dimensionless number is most commonly kept constant to ensure similar mixing characteristics?
Reynolds number
Péclet number
Froude number
Mach number
Explanation - Keeping Reynolds number constant maintains similar flow regimes and mixing efficiency across scales.
Correct answer is: Reynolds number
Q.45 Which of the following is a key advantage of using a micro‑fluidic bioreactor for drug screening?
Higher throughput with minimal reagent consumption
Ability to operate at extreme pressures
Simplified sterilization procedures
Greater resistance to contamination
Explanation - Micro‑fluidic platforms enable parallel testing of many conditions using tiny volumes, accelerating drug discovery.
Correct answer is: Higher throughput with minimal reagent consumption
Q.46 In a bioreactor used for algae biofuel production, which electrical measurement can be used to estimate biomass concentration indirectly?
Impedance spectroscopy
Voltage ripple analysis
Current harmonics
Phase‑locked loop frequency
Explanation - Changes in electrical impedance correlate with cell density, providing a non‑invasive biomass estimate.
Correct answer is: Impedance spectroscopy
Q.47 What is the primary purpose of adding a buffer solution to the culture medium in a bioreactor?
To increase electrical conductivity
To maintain a stable pH during metabolic activity
To enhance oxygen solubility
To reduce shear forces
Explanation - Buffers resist pH changes caused by metabolic by‑products, protecting cell physiology.
Correct answer is: To maintain a stable pH during metabolic activity
Q.48 Which type of motor is most commonly used for large‑scale bioreactor agitation due to its reliability and efficiency?
Brushed DC motor
Stepper motor
Synchronous AC motor
Servo motor
Explanation - Synchronous AC motors deliver constant speed and high efficiency, suitable for continuous industrial agitation.
Correct answer is: Synchronous AC motor
Q.49 In a bioprocess producing a recombinant protein, why might a researcher add a metal ion chelator such as EDTA to the medium?
To increase the conductivity of the medium
To inhibit proteases that require metal cofactors
To boost dissolved oxygen levels
To raise the temperature of the culture
Explanation - EDTA binds metal ions, deactivating metalloproteases that could degrade the target protein.
Correct answer is: To inhibit proteases that require metal cofactors
Q.50 What is a common method for sterilizing a bioreactor before use?
Microwave irradiation
Autoclaving (steam sterilization)
UV‑C exposure
Chemical vapor deposition
Explanation - Steam at 121 °C for a set duration reliably kills microorganisms and spores in the reactor.
Correct answer is: Autoclaving (steam sterilization)
Q.51 When using a bioreactor for the production of virus‑like particles (VLPs), which downstream step is essential before formulation?
Centrifugation to remove cell debris
Electroporation of the culture
pH adjustment to 3.0
Freezing the entire broth
Explanation - Clarification by centrifugation separates VLPs from cells and debris, facilitating purification.
Correct answer is: Centrifugation to remove cell debris
Q.52 Which factor most influences the selection of the impeller type for a bioreactor used in shear‑sensitive cell cultures?
Impeller diameter
Blade angle
Low shear design (e.g., marine impeller)
Material of construction
Explanation - Marine or pitched‑blade impellers generate gentle mixing, minimizing damage to delicate cells.
Correct answer is: Low shear design (e.g., marine impeller)
Q.53 Which of the following is a typical use of a bioreactor in the field of regenerative medicine?
Large‑scale production of antibiotics
Expansion of stem cells for therapeutic implantation
Generation of synthetic polymers
Purification of heavy metals
Explanation - Bioreactors provide controlled environments to grow sufficient numbers of stem cells for clinical use.
Correct answer is: Expansion of stem cells for therapeutic implantation
Q.54 In an electrically powered bioreactor, what is the purpose of a power factor correction (PFC) circuit?
To improve the efficiency of AC‑DC conversion and reduce reactive power draw
To increase the temperature of the culture
To stabilize pH
To control the speed of the impeller
Explanation - PFC minimizes phase shift between voltage and current, lowering energy losses and meeting utility regulations.
Correct answer is: To improve the efficiency of AC‑DC conversion and reduce reactive power draw
Q.55 Which of the following bioreactor designs is most suitable for culturing mammalian cells in suspension at high densities?
Air‑lift reactor
Stirred‑tank reactor with wave motion
Packed‑bed reactor
Bubble column reactor
Explanation - Air‑lift reactors provide low shear and efficient oxygen transfer, ideal for high‑density mammalian cultures.
Correct answer is: Air‑lift reactor
Q.56 During a fed‑batch process, why is it important to monitor the dissolved oxygen trend after each feed addition?
To ensure the feed has been fully mixed
To detect increased metabolic activity that may consume more oxygen
To measure the pH shift caused by the feed
To verify the temperature of the feed solution
Explanation - Feeding substrate often accelerates cell metabolism, raising oxygen demand; monitoring avoids oxygen limitation.
Correct answer is: To detect increased metabolic activity that may consume more oxygen
Q.57 What is the main advantage of using a dual‑sensor (pH and dissolved O₂) probe with integrated temperature compensation?
Reduced wiring complexity
More accurate readings across varying temperatures
Lower cost compared to separate probes
Ability to measure CO₂ simultaneously
Explanation - Temperature affects electrode response; integrated compensation ensures reliable measurements.
Correct answer is: More accurate readings across varying temperatures
Q.58 Which of the following best describes the principle of 'scale‑down' modeling in bioprocess engineering?
Running a full‑scale process at reduced temperature
Creating a small‑volume reactor that mimics the hydrodynamic and mass‑transfer conditions of a large reactor
Using a lower power supply for the same reactor
Decreasing the number of sensors to simplify control
Explanation - Scale‑down models allow rapid testing of process parameters while preserving critical physical phenomena.
Correct answer is: Creating a small‑volume reactor that mimics the hydrodynamic and mass‑transfer conditions of a large reactor
Q.59 In a bioreactor designed for the production of a recombinant enzyme, which of the following could be a reason to switch from batch to fed‑batch mode?
To increase the final substrate concentration
To prevent substrate inhibition and extend the productive phase
To reduce the need for temperature control
To lower the oxygen transfer rate
Explanation - Fed‑batch allows controlled addition of substrate, avoiding inhibitory concentrations while maintaining growth.
Correct answer is: To prevent substrate inhibition and extend the productive phase
Q.60 Which type of bioreactor is commonly employed for the production of plasma‑derived proteins using mammalian cell lines?
Air‑lift reactor
Perfusion bioreactor with cell retention
Packed‑bed reactor
Batch reactor with static culture
Explanation - Perfusion maintains high cell densities and continuous product harvest, increasing yields of plasma‑like proteins.
Correct answer is: Perfusion bioreactor with cell retention
Q.61 When integrating a PLC (Programmable Logic Controller) into a bioreactor control system, which communication protocol is most widely used in industrial automation?
USB
Bluetooth
Modbus TCP/IP
Wi‑Fi Direct
Explanation - Modbus is a robust, open‑standard protocol for reliable data exchange between PLCs and sensors/actuators.
Correct answer is: Modbus TCP/IP
Q.62 In a bioreactor used for the production of a bacterial endotoxin‑free protein, why is it critical to monitor and control the endotoxin level?
Endotoxins increase the viscosity of the broth
Endotoxins can cause severe immune reactions in patients receiving the product
Endotoxins affect the pH of the medium
Endotoxins improve cell growth
Explanation - Regulatory standards require minimal endotoxin levels to ensure safety of biopharmaceuticals.
Correct answer is: Endotoxins can cause severe immune reactions in patients receiving the product
Q.63 Which electrical phenomenon can cause inaccurate pH sensor readings in a bioreactor if not properly shielded?
Electromagnetic interference (EMI)
Electrostatic discharge (ESD)
Resonant frequency shift
Capacitive coupling
Explanation - EMI can induce noise in the low‑level signals from pH electrodes, leading to erroneous readings.
Correct answer is: Electromagnetic interference (EMI)
Q.64 What is the main function of a back‑pressure regulator in a bioreactor gas‑delivery system?
To increase the temperature of the incoming gas
To maintain a constant gas flow rate irrespective of pressure fluctuations
To filter out contaminants from the gas
To measure dissolved oxygen
Explanation - Back‑pressure regulators stabilize pressure, ensuring consistent sparging rates.
Correct answer is: To maintain a constant gas flow rate irrespective of pressure fluctuations
Q.65 In a bioreactor used for the synthesis of a therapeutic peptide, why might a researcher opt for a continuous flow reactor instead of a batch system?
Continuous flow offers better temperature control and higher product purity
Batch reactors cannot be sterilized
Continuous flow reduces the need for sensors
Batch reactors are not compatible with peptides
Explanation - Steady conditions in continuous flow improve reaction specificity and simplify downstream purification.
Correct answer is: Continuous flow offers better temperature control and higher product purity
Q.66 Which material is preferred for constructing electrodes used in electro‑stimulated tissue culture bioreactors?
Copper
Stainless steel
Platinum or gold
Aluminum
Explanation - Noble metals resist corrosion and do not release toxic ions, maintaining a biocompatible environment.
Correct answer is: Platinum or gold
Q.67 What is the role of an 'oxygen probe calibration' routine before a bioprocess run?
To set the pH setpoint
To adjust the impeller speed
To ensure accurate dissolved oxygen measurements by establishing zero and saturation points
To program the feeding schedule
Explanation - Calibration aligns probe output with known oxygen concentrations, enabling reliable monitoring.
Correct answer is: To ensure accurate dissolved oxygen measurements by establishing zero and saturation points
Q.68 During a bioreactor run for vaccine antigen production, a sudden rise in temperature is observed. Which electrical component is most likely responsible?
Faulty temperature sensor
Overheating drive motor for the impeller
Damaged pH electrode
Blocked gas sparger
Explanation - Motor inefficiencies can generate excess heat, raising the reactor temperature if not properly cooled.
Correct answer is: Overheating drive motor for the impeller
Q.69 In a bioreactor used for production of a recombinant virus, which biosafety measure is essential to prevent aerosol release?
Using a sealed, HEPA‑filtered exhaust system
Operating at low temperature
Adding antifoam agents
Increasing impeller speed
Explanation - HEPA filtration captures viral particles, preventing environmental contamination.
Correct answer is: Using a sealed, HEPA‑filtered exhaust system
Q.70 Which of the following is a common challenge when using a large‑scale bioreactor for the production of a temperature‑sensitive enzyme?
Maintaining uniform temperature throughout the vessel
Achieving sufficient mixing
Providing enough lighting
Reducing magnetic fields
Explanation - Heat generated by metabolism and equipment can create gradients; uniform temperature is critical for enzyme stability.
Correct answer is: Maintaining uniform temperature throughout the vessel
Q.71 What is the primary purpose of using a 'soft start' function on the motor driving a bioreactor impeller?
To gradually ramp up the voltage and reduce mechanical stress on the system
To increase the dissolved oxygen instantly
To change the pH setpoint automatically
To sterilize the impeller
Explanation - Soft start minimizes inrush current and protects mechanical components from shock loads.
Correct answer is: To gradually ramp up the voltage and reduce mechanical stress on the system
Q.72 When designing a bioreactor for the cultivation of electroactive bacteria, which electrical characteristic of the system must be carefully managed?
Circuit resistance to avoid short circuits
Electrode potential to control microbial electron transfer
Capacitance for signal filtering
Inductive reactance for motor control
Explanation - Electroactive microbes interact with electrodes; precise potential control influences metabolism and product formation.
Correct answer is: Electrode potential to control microbial electron transfer
Q.73 Which analytical method can be integrated online to monitor the concentration of a secreted protein in a bioreactor broth?
High‑performance liquid chromatography (HPLC)
Surface plasmon resonance (SPR) sensor
Mass spectrometry (MS)
Western blot
Explanation - SPR provides label‑free, real‑time detection of specific proteins directly in the culture fluid.
Correct answer is: Surface plasmon resonance (SPR) sensor
Q.74 In a bioreactor used for cell‑based therapies, why is a closed‑system design preferred?
To reduce the need for temperature control
To minimize contamination risk and maintain sterility
To increase the speed of agitation
To allow easier visual inspection
Explanation - Closed systems protect the product from environmental microbes, crucial for clinical applications.
Correct answer is: To minimize contamination risk and maintain sterility
Q.75 Which factor most directly influences the oxygen transfer coefficient (kLa) in a stirred‑tank bioreactor?
Impeller type and speed
pH setpoint
Medium viscosity only
Temperature of the cooling jacket
Explanation - kLa depends on mixing intensity and gas‑liquid interfacial area, both affected by impeller design and rotation rate.
Correct answer is: Impeller type and speed
Q.76 What is a key benefit of using a wireless sensor network (WSN) for monitoring multiple parameters in a bioreactor facility?
Eliminates the need for any calibration
Allows real‑time data collection without extensive wiring, reducing contamination risk
Provides higher accuracy than wired sensors
Increases the power consumption of the system
Explanation - WSNs simplify installation and maintenance while keeping the bioprocess area sterile.
Correct answer is: Allows real‑time data collection without extensive wiring, reducing contamination risk
Q.77 During scale‑up of a bioreactor, which parameter is most likely to change, requiring redesign of the control system?
Number of electrodes
Signal transmission delay (dead time)
Color of the reactor vessel
Type of magnetic stir bar
Explanation - Larger systems have longer wiring and sensor distances, increasing dead time that can affect controller performance.
Correct answer is: Signal transmission delay (dead time)
Q.78 Which bioreactor configuration is typically employed for the production of virus‑like particles that require high‑shear mixing for virus assembly?
Wave‑motion bioreactor
Stirred‑tank bioreactor with high‑shear impeller
Air‑lift reactor
Packed‑bed reactor
Explanation - High shear can promote proper assembly of viral capsid components, enhancing VLP yield.
Correct answer is: Stirred‑tank bioreactor with high‑shear impeller
Q.79 In a bioreactor used for the production of a biodegradable polymer, which analytical technique is most suitable for monitoring monomer concentration in real time?
Raman spectroscopy
Fluorescence microscopy
Flow cytometry
Electrophoresis
Explanation - Raman provides rapid, non‑invasive detection of specific chemical bonds, enabling real‑time monomer tracking.
Correct answer is: Raman spectroscopy
Q.80 Why might a researcher employ a 'dead‑time compensation' algorithm in the PID controller of a bioreactor?
To speed up data logging
To improve stability and response despite sensor‑to‑controller delay
To reduce the power consumption of the heater
To increase the impeller speed automatically
Explanation - Compensation predicts future error, mitigating the destabilizing effect of dead time on the control loop.
Correct answer is: To improve stability and response despite sensor‑to‑controller delay
Q.81 Which type of bioreactor is most appropriate for the large‑scale production of a recombinant protein that requires glycosylation?
Stirred‑tank bioreactor with CHO cells
Anaerobic digester
Photobioreactor with algae
Packed‑bed reactor with bacteria
Explanation - Mammalian CHO cells perform complex post‑translational modifications like glycosylation needed for many therapeutics.
Correct answer is: Stirred‑tank bioreactor with CHO cells
Q.82 What is the main purpose of using a 'back‑mixing' zone in a continuous stirred‑tank reactor (CSTR) for bioprocessing?
To create a temperature gradient
To ensure uniform composition and prevent dead zones
To increase the pH variability
To reduce the need for sensors
Explanation - Back‑mixing promotes homogeneity, essential for consistent product quality in continuous processes.
Correct answer is: To ensure uniform composition and prevent dead zones
Q.83 In the context of bioreactor safety, what does the acronym 'NFPA' stand for?
National Federation of Power Appliances
National Fire Protection Association
Nanotechnology Fabrication and Processing Association
Neutral Flow Pressure Analyzer
Explanation - NFPA provides standards (e.g., NFPA 45) for fire protection in chemical and bioprocessing facilities.
Correct answer is: National Fire Protection Association
Q.84 Which of the following best explains why a bioreactor used for the production of an antibody drug may operate at a lower temperature (e.g., 32 °C) compared to typical bacterial cultures (37 °C)?
Lower temperature reduces the risk of contamination
Mammalian cells producing antibodies often have optimal growth and protein folding at sub‑physiological temperatures
It minimizes oxygen consumption
It speeds up the fermentation process
Explanation - Reduced temperature can improve protein quality and stability while maintaining cell viability.
Correct answer is: Mammalian cells producing antibodies often have optimal growth and protein folding at sub‑physiological temperatures
Q.85 Which of the following sensors would be least appropriate for direct measurement of cell density in a high‑viscosity bioreactor broth?
Optical density probe
Ultrasonic (acoustic) sensor
Capacitive biomass sensor
Thermocouple
Explanation - Thermocouples measure temperature, not cell concentration; the others can infer biomass even in viscous media.
Correct answer is: Thermocouple
Q.86 During the production of a recombinant viral vector, why is it important to monitor the pH trend after the addition of a base for neutralization?
To ensure the base does not cause precipitation of media components
To verify that the temperature remains constant
To confirm that the impeller speed is adequate
To detect a possible shift that could affect viral stability
Explanation - pH fluctuations can inactivate viral particles or affect their assembly; monitoring ensures product integrity.
Correct answer is: To detect a possible shift that could affect viral stability
Q.87 What is the primary reason for employing a 'closed‑loop' control system rather than an 'open‑loop' system in a bioreactor used for cell therapy production?
Closed‑loop systems are cheaper
Closed‑loop systems automatically adjust to disturbances, maintaining critical parameters within tight limits
Open‑loop systems require more sensors
Open‑loop systems cannot be automated
Explanation - Closed‑loop feedback corrects deviations in real time, essential for the stringent quality requirements of cell therapies.
Correct answer is: Closed‑loop systems automatically adjust to disturbances, maintaining critical parameters within tight limits
Q.88 Which of the following is a typical consequence of insufficient mixing in a large‑scale bioreactor?
Uniform temperature distribution
Localized nutrient depletion and pH gradients
Improved oxygen transfer
Reduced foam formation
Explanation - Poor mixing leads to zones where cells experience different conditions, negatively affecting growth and product consistency.
Correct answer is: Localized nutrient depletion and pH gradients
Q.89 In a bioreactor for the production of a recombinant enzyme, which electrical measurement can be used as an indirect indicator of cell growth rate?
Current draw of the heating element
Voltage across the pH probe
Impedance of the culture medium
Frequency of the motor drive
Explanation - Cell density changes the electrical properties of the broth; impedance spectroscopy can correlate with biomass.
Correct answer is: Impedance of the culture medium
Q.90 Why is it important to perform a 'sanitary design review' of a bioreactor before commissioning?
To verify compliance with electromagnetic compatibility standards
To ensure the design prevents microbial ingress and facilitates cleaning
To reduce the weight of the reactor
To improve the visual aesthetics of the plant
Explanation - Sanitary design minimizes contamination risk and allows effective CIP (clean‑in‑place) procedures.
Correct answer is: To ensure the design prevents microbial ingress and facilitates cleaning
Q.91 Which type of control algorithm is best suited for maintaining a constant substrate feed rate despite disturbances in a fed‑batch bioprocess?
On‑off control
Model predictive control (MPC)
Bang‑bang control
Manual feed adjustment
Explanation - MPC predicts future process behavior and optimizes feed rates while handling constraints and disturbances.
Correct answer is: Model predictive control (MPC)
Q.92 In the production of a biosimilar monoclonal antibody, what is the main regulatory reason for implementing real‑time monitoring of critical quality attributes (CQAs) in the bioreactor?
To reduce the cost of raw materials
To ensure the product meets predefined specifications throughout the run
To speed up the agitation speed
To increase the reactor pressure
Explanation - Real‑time CQA monitoring enables immediate corrective actions, supporting regulatory compliance and product safety.
Correct answer is: To ensure the product meets predefined specifications throughout the run
Q.93 Which of the following is a common method for reducing the risk of contamination when scaling up a bioprocess from bench to pilot scale?
Increasing the impeller size
Using single‑use disposable bioreactor bags
Operating at higher temperature
Adding more antifoam agents
Explanation - Disposable systems eliminate cleaning steps that could introduce contaminants, simplifying scale‑up.
Correct answer is: Using single‑use disposable bioreactor bags